1. Field of the Invention
The present invention broadly relates to handling of folded box blanks glued only at bottom portions thereof and, hence, having different thicknesses at opposite ends thereof. More particularly, the invention is concerned with an apparatus for stacking such folded box blanks in such a manner that alternating groups of a predetermined number of blanks are inverted through 180.degree., i.e., in such a manner that the head portions of the blanks of one group are placed directly over the bottom portions of the blanks of an underlying group of blanks.
2. Description of the Prior Art
In the field of box production wherein the boxes are made of, for example, cardboard sheet, it is common practice to fold a box blank which is glued only at the bottom portion thereof and to stack a plurality of folded box blanks in layers before they are delivered. As is well known, such a blank can easily be set up in the form of a box which is ready for convenient use.
A problem is encountered in this process in that each folded blank has a difference in thickness between the bottom portion which is glued together and the top portion which is not glued so that the difference in the thickness is multiplied when a plurality of such blanks are stacked in the same orientation with the result that a large difference in height is created between opposite ends of the stack or the stack is rendered unstable. In order to eliminate this problem, it is necessary to periodically change the orientation of the blanks by inverting the blanks through a rotation of 180.degree. for a predetermined number of blanks, e.g., blanks in an upper half of a stack have an orientation which is opposite to that of the blanks in the lower half of the stack.
In order to satisfy such a demand, an apparatus has been proposed which is capable of effecting such inverting of the folded box blanks. This apparatus can conveniently be incorporated in a system for making boxes in such a manner that the process includes a step of periodically changing the orientation of the stacked blanks.
In general, a process for making boxes from a sheet material such as cardboard includes a step of conveying blanks by means of a conveyor. It has therefore been proposed to incorporate a mechanism which is designed to change the orientation of the blanks such that alternating groups of blanks which are being successively conveyed by a conveyor are oriented in opposite directions. Unfortunately, however, the known mechanisms for accomplishing this result require an excessive time for inverting the blanks and yet fail to smoothly invert the blanks.